1. Field of the Invention
The invention is in the field of preparing ethylidene bisformamide from acetaldehyde and formamide, and, optionally thereafter, cracking (thermally decomposing) the ethylidene bisformamide to N-vinylformamide. This invention also relates to a chemical process for forming poly(vinylamine) salts of mineral acids, especially poly(vinylamine hydrochloride) from the resulting N-vinylformamide.
2. Description of the Prior Art
Poly(vinylamine), its salts, and products based thereon are desirable chemicals. Efficient and effective integrated overall processes for the production of poly(vinylamine) salts and poly(vinylamine) itself, of course, would encourage and promote the widespread commercial use of said chemicals. U.S. Pat. No. 4,018,826, issued on Apr. 19, 1977, to Richard Gless, Daniel J. Dawson, and Robert E. Wingard, discloses a process for preparing poly(vinylamine) wherein acetaldehyde and acetamide are formed into ethylidene-bisacetamide which is then cracked to yield vinylacetamide which is polymerized and hydrolyzed to poly(vinylamine). In said patent, acetaldehyde and acetamide are reacted in a liquid phase in the presence of an aqueous strong liquid mineral acid.
In U.S. Pat. No. 4,176,136, issued on Nov. 27, 1979 to Daniel J. Brenzel, an improved method for carrying out this reaction is disclosed wherein ethylidene-bisacetamide is prepared by the process of contacting a liquid mixture of acetaldehyde and acetamide with a solid cation exchange resin at a temperature of from about 10.degree. C. to about 110.degree. C.
Other references to the condensation reaction of acetaldehyde and acetamide in the prior art include V. V. Richter, Ber. 5,477(1877); W. Noyes et al, J. Am. Chem. Soc., 55,3493 (1933) and Ben Ishai et al, Tetrahedron Letters, 50,4523 (1965). Also, a general review article on the condensation of aldehydes and amines may be found in Organic Reactions, 14,52 (1965).
An effective and efficient process for producing poly(vinylamine) salts in good yields beginning with formamide, however, has heretofore not been known. Indeed, the sole references known to us regarding even the preparation ethylidene bisformamide, Keimmel, et al; J. Org. Chem., 36, 350 (1971), and Takase, et al, Sci.Rep. (Osaka), 16(1), 7 (1967) shows very mediocre yields. Similarly, when acetamide is merely replaced by formamide in the Gless et al or Brenzel processes, a usable product is not obtained. Rather, a low yield dark-colored degraded product is generally the result.
It is an object of the instant invention to provide an effective process for producing ethylidene bisformamide from formamide and acetaldehyde.